1. Field of the Invention
The present invention relates to a method for manufacturing a semiconductor device, and more particularly, to a thermal treating method of a silicon wafer.
2. Description of the Background Art
As a semiconductor device is miniaturized, the time of thermal treatment applicable to the semiconductor device is shortened in recent years. To this end, rapid thermal annealing (RTA), typical of which is lamp annealing, has now been in wide use to thermally treat a semiconductor device. According to RTA, a semiconductor device is, for example, subjected to thermal annealing at a high temperature exceeding 1000xc2x0 C. within a short time, by which a desired thermal annealing effect can be expected without damaging the semiconductor device.
The thermal treatment for a semiconductor device may be sometimes carried out in such a state that silicon is exposed at the surface of a wafer. In the step of forming a transistor, for example, after a gate electrode, which includes a built-up film of a doped polysilicon (D-poly film) and a tungsten silicide film (W-Si film), has been formed on a gate insulating film, the thermal treatment may be carried out under such conditions that the D-poly film and the W-Si film are exposed at the side surfaces of the gate electrode.
When a check is made for the surface condition of the wafer in which silicone is exposed at the surface thereof after thermal treatment at high temperatures of 1000xc2x0 C. or over according to lamp annealing, it has been found that a number of minute foreign matters with a diameter of approximately 0.1 xcexcm are observed on the wafer surface. Such minute foreign matters will cause the failure of a semiconductor device if the further scale down of the device is intended.
It is accordingly an object of the invention to provide a method for manufacturing a semiconductor device, which overcomes the problems involved in the prior art.
It is another object of the invention to provide a method for manufacturing a semiconductor device wherein a wafer having exposed silicon at the surfaces thereof is thermally treated without causing the occurrence of minute foreign matters.
The above objects of the present invention are achieved by a method for manufacturing a semiconductor device described below. In the method, there is transferred a wafer having an exposed portion of silicon to a thermal treatment chamber. An atmosphere of the thermal treatment chamber is converted to a reduced pressure atmosphere of an inert gas. The wafer is subjected to thermal treatment in the reduced pressure atmosphere of an inert gas
Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.